Which parasite egg may not be detected in zinc flotation procedures?

Which parasite egg may not be detected in zinc flotation procedures?

• A. Schistosoma mansoni
• B. Ascaris lumbricoides
• C. Trichuris trichiura
• D. Taenia saginata

Answer: (A)

In fecal parasite testing, flotation relies on buoyancy: eggs with a lower density than the flotation solution rise to the surface, while denser eggs sink. Schistosoma mansoni eggs are too dense to float in standard zinc sulfate flotation solutions, so they are frequently missed when relying on flotation alone. Detecting these eggs is better achieved with sedimentation or concentration methods (such as formalin-ethyl acetate sedimentation) or other direct stool techniques. Other common helminth eggs like Ascaris lumbricoides, Trichuris trichiura, and Taenia saginata generally float in zinc sulfate solutions and are more readily detected by this method.

In fecal parasite testing, flotation relies on buoyancy: eggs with a lower density than the flotation solution rise to the surface, while denser eggs sink. Schistosoma mansoni eggs are too dense to float in standard zinc sulfate flotation solutions, so they are frequently missed when relying on flotation alone. Detecting these eggs is better achieved with sedimentation or concentration methods (such as formalin-ethyl acetate sedimentation) or other direct stool techniques. Other common helminth eggs like Ascaris lumbricoides, Trichuris trichiura, and Taenia saginata generally float in zinc sulfate solutions and are more readily detected by this method.